By now you must have come across websites (multiple times) that allow you to log into their system using your Twitter, Facebook and Google credentials. This way, you don’t exclusively have to register on these websites. Since most of us are already logged into our Google, Facebook and Twitter accounts while surfing the Internet (make sure you don’t do it on publicly accessible computers), it is easier to use the same credentials in order to log into other systems also.
Well, now you can do it on your WordPress blog also. Whenever somebody wants to leave a comment he or she either leaves it anonymously, or needs to register first and then log into your blog commenting system. This deters many people from leaving comments on your blog. On the other hand if they can simply use their Facebook, Twitter or Google accounts to login it will be much easier for them to leave comments on your blog.
And like many websites, WordPress doesn’t come with its own built in capability to let your users log into your command system using Twitter etc. But there are many plug-ins you can use. Some of such plug-ins are reviewed and explained in this blog post on onextrapixel.